test/nvmf: remove shebang from the common file

The file is not meant to be executed, so shebang is
not needed - let's remove it.

Change-Id: I51c32613ffb25b43a2d1b96523a8f25c853594e4
Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/461355


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>